I had a battery replaced on my 'retired' iPhone 7Plus and have set up the phone to fill a need for a 'standby' or 'guest phone' to save family or friends visiting here the costs of roaming if using their own devices. The local phone is on a local sim for a number I've long had, and is strictly pay-as-you-go, easily topped up online with our carrier. The other (self & wife's) phones are on postpaid accounts and handled differently. Having had minor issues in the past with synch happening when not wanted, I decided to do it right and it was suggested that I establish a totally separate Apple ID for this phone alone, totally avoiding any problems with contacts synching where they shouldn't etc and only keeping really needed contacts stored on the phone ( home land-line, my cell, wife's cell) leaving anyone using it onky the option of keypad dialing, and of course receiving calls. There is never access provided to data on our primary accounts or devices. The shop ( authorized Apple Reseller) did the battery change, wiped the phone and set up as new suggesting that I supply a different email address & password than either of my primary email addresses to keep it all painless. I thus use my Yahoo email for things like this. ( My primary email addresses are Gmail & or iCloud. All good, but he did use my first and last name for that ID, as it's what's on thier files for me. It was mostly an oversight on my part at the time, and the shop was busy. After the fact, can I edit simply the name, leaving the email & password as what was established in the new phone at that time. I've done the rest of the set up and will not link that ID to any payment method, and use the 'local' address ( Barbados) for it as opposed to my regular use of the Canadian App store for our main phones. That way, paths should never get crossed or tangled as the ecosystem can get complex at times if things get interchanged. I se up the Apple canned mail in the 'guest phone' also to the yahoo address to facilitate moving anything to and from the phone easily.